The present invention relates to a two-color radiation thermometer for measuring a temperature of an object in a non-contact mode using thermal radiation from the object.
A two-color radiation thermometer (two-wavelength radiation thermometer) has been used for measuring a temperature of, for example, combustion or explosion inside a blast furnace in a non-contact mode (refer to Japanese Patent Publication (Kokai) No. 07-253361). Particularly, when a measuring object has a two-dimensional surface, a two-color radiation thermometer with a CCD camera is useful (refer to Japanese Patent Publication (Kokai) No. 2002-309307). In such a two-color radiation thermometer, the CCD camera captures an image of a measuring surface using two different wavelengths, so that it is possible to calculate a two-dimensional temperature distribution of the measuring surface based on a difference of two images in brightness information.
In such a tow-color radiation thermometer, as a method of obtaining images corresponding to two wavelengths, there has been a method in which two CCD cameras independently receive light separated by a wavelength selective prism (two-plate system). As disclosed in Japanese Patent Publication (Kokai) No. 2002-309307, there has been another method in which a RGB filter, ordinarily used as a CCD sensor for regular color photography, is provided for selecting a wavelength without an optical device such as a prism (single-plate system).
In the two-plate system, it is possible to freely select a measuring wavelength through changing the prism or the wavelength selective filter. However, it is necessary to provide two CCD cameras, thereby making the device complicated and increasing cost. On the other hand, in the single-plate system, it is possible to make the device simple and reduce cost. However, since the CCD sensor for regular color photography is used, it is difficult to select a measuring wavelength other than the three wavelengths, i.e. red, green, and blue (RGB). Accordingly, it is difficult to measure an accurate temperature depending on a color of light (wavelength) emitted from a measuring object.
In view of the problems described above, the present invention has been made, and an object of the present invention is to provide a two-color radiation thermometer capable of freely and easily selecting a measuring wavelength with a simple configuration such as the single-plate system.
Further objects and advantages of the invention will be apparent from the following description of the invention.